Industrial hemp which contains little to no psychoactive compounds like Tetrandryocannabinol (THC) has many uses. The seeds can make up as much as half of the weight of the whole plant and about ⅓ of the seed weight is composed of hemp oil, which is rich in omega-3 fatty acids and ¼ by weight protein. The oil and whole seeds are used as a dietary supplement. The outside part of the stalk or fiber of the plant can be used to make rope, paper, and fiberboard. The stalk contains Cannabidiolic Acid (CBDa) in concentrations as low as 1-6% with some experimental varieties containing more. CBDa has little to no medicinal properties whereas its decarboxylated counterpart Cannabidiol (CBD) has many. CBDa can be decarboxylated to make CBD. The most common methods for doing this is to first extract the hemp stalks (biomass) with a solvent like high pressure super critical CO2, liquid CO2 or an organic solvent such as a lower (C1-C4) alcohol, e.g., methanol, ethanol, propanol or butanol. The resulting hemp extract can contain about 3% to 35% CBDa depending on the variety and this extract is typically heated to temperatures as high as 140° C. for several hours to decarboxylate the CBDa to form CBD. The conversion efficiency of this step is about 78-80% in the lab and 60-70% commercially. In order to reach these high temperatures, special heating equipment is required and the largest batch size for this heating equipment is typically quite small, around 200-kg.
There is a real need to be able to decarboxylate hemp extract at lower temperatures, 100° C. or less, and in larger batch sizes. Low temperature decarboxylation would not need any special heating equipment and could be performed in most industrial plants were heating with steam is common.
There is also a need to decarboxylate the CBDa in hemp biomass. If this could be done, then one could simply extract the biomass at low pressure liquid CO2 and collect the CBD without having to further process the hemp extract.